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Biomedical subjects

Ryoichi Nakamura

Publications and source records attributed to Ryoichi Nakamura.

16 recordsLinked to original sources
PubMed2007

[Information guided technology and procedure in neurosurgical field].

Translational Research is the research to apply and mediate a fundamental research result to the clinical field effectively. The integration of the diagnosis and the treatment is an important item in the life science field from the viewpoint of quality of therapy and minimally invasive therapy. The standardization of mechanical interface of the medicine related machine, system and a medical information system are important from the viewpoint such as prevention of medical malpractice. A high function operating robot (manipulator) as an endoscopic robot and image-guided minimally invasive device are important in the point of view of the development of a medical device shown with a medical device industry vision. We describe an outline of our ongoing development of endoscope system, intraoperative MRI (intelligent operating theater) and robot surgery system in neurosurgical field.

Humans↗
PubMed2006

New radiofrequency coil integrated with a stereotactic frame for intraoperative MRI-controlled stereotactically guided brain surgery.

Mislocalization errors caused by MR image distortions or brain shift are one of the main causes of complications after stereotactically guided neurosurgical procedures. A special device, which could ameliorate such effects and provide intraoperative acquisition of MR images of sufficient diagnostic accuracy, was developed. It is composed of a radiofrequency receiver coil integrated with a modified Komai stereotactic frame and a Sugita four-pin head holder. Clinical testing revealed that the use of the device during stereotactically guided procedures under the control of low magnetic field strength (0.3 T) intraoperative MRI ameliorates the effects of brain shift, and permits to obtain informative tissue samples and to perform aggressive removal of the lesion without any damage of the eloquent cerebral structures. The possibility of an easy shift from a stereotactically guided to a routine microneurosurgical procedure represents an additional benefit of the developed device.

Adolescent↗
PubMed2006

Drosophila damaged DNA binding protein 1 contributes to genome stability in somatic cells.

The damaged DNA-binding protein (DDB) complex consists of a heterodimer of p127 (DDB1) and p48 (DDB2) subunits and is believed to have a role in nucleotide excision repair (NER). We used the GAL4-UAS targeted expression system to knock down DDB1 in wing imaginal discs of Drosophila. The knock-down was achieved in transgenic flies using over-expression of inverted repeat RNA of the D-DDB1 gene [UAS-D-DDB1(650)-dsRNA]. As a consequence of RNA interference (RNAi), the fly had a shrunken wing phenotype. The wing spot test showed induced genome instability in transgenic flies with RNAi knock-down of D-DDB1 in wing imaginal discs. When Drosophila larvae with RNAi knock-down of D-DDB1 in wing imaginal discs were treated with the chemical mutagen methyl methanesulfonate (MMS), the frequency of flies with a severely shrunken wing phenotype increased compared to non-treated transgenic flies. These results suggested that DDB1 plays a role in the response to DNA damaged with MMS and in genome stability in Drosophila somatic cells.

Animals↗
PubMed2006

Characterization of a second proliferating cell nuclear antigen (PCNA2) from Drosophila melanogaster.

The eukaryotic DNA polymerase processivity factor, proliferating cell nuclear antigen, is an essential component in the DNA replication and repair machinery. In Drosophila melanogaster, we cloned a second PCNA cDNA that differs from that encoded by the gene mus209 (for convenience called DmPCNA1 in this article). The second PCNA cDNA (DmPCNA2) encoded a 255 amino acid protein with 51.7% identity to DmPCNA1, and was ubiquitously expressed during Drosophila development. DmPCNA2 was localized in nuclei as a homotrimeric complex and associated with Drosophila DNA polymerase delta and epsilonin vivo. Treatment of cells with methyl methanesulfonate or hydrogen peroxide increased the amount of both DmPCNA2 and DmPCNA1 associating with chromatin, whereas exposure to UV light increased the level of association of only DmPCNA1. Our observations suggest that DmPCNA2 may function as an independent sliding clamp of DmPCNA1 when DNA repair occurs.

Amino Acid Sequence↗
PubMed2005

Stereoselective synthesis of premisakinolide A, the monomeric counterpart of the marine 40-membered dimeric macrolide misakinolide A.

[structure: see text] The first synthesis of premisakinolide A, the monomeric counterpart of misakinolide A, the marine 40-membered macrolide displaying potent activity against a variety of human carcinoma cell lines, has been reported. The strategy was highlighted by a crucial coupling of a tetrahydropyran fragment and an alkynylaluminum reagent having a polypropionate chain, the highly stereoselective cross aldol reaction of segment A and segment B, and the stereospecific construction of the polypropionate structure based on original acyclic stereocontrol.

Animals↗
PubMed2005

Intelligent operating theater using intraoperative open-MRI.

Malignant brain tumors vary among patients and are characterized by their irregular shapes and infiltration. Localization of functional areas in the brain also differs among patients, and excess removal of tumor near eloquent areas may increase the risk of damage of function, such as motor paresis and speech disturbance. Recent progress in magnetic resonance (MR) imaging technology has enabled acquisition of intraoperative images and totally changed the neurosurgery of malignant brain tumors. Before, surgeons could merely speculate about the results of surgical manipulation and have no certainty about procedure outcomes until postoperative examination. Because intraoperative MR images allow visualization of the size of residual tumor(s) and the positional relationship between the tumor(s) and eloquent areas, surgeons are now able to achieve safe and reliable surgery. As an example, positional error on preoperative MR images caused by shifting of the brain (brain shift), a long-standing annoyance for surgeons, has been resolved using intraoperative MR images for surgical navigation, allowing precise resection. Two types of open-MR imaging scanner, a 0.2- or 0.3-tesla hamburger-type scanner with a horizontal gap and a 0.12- or 0.5-tesla double doughnut-type scanner with a vertical gap, are now available in the operating theater, and 1.5-tesla bore-type scanners are available. A 3.0-tesla bore-type scanner is planned. Intraoperative MR imaging includes diffusion-tensor and diffusion-weighted imaging, which allows visualization of nerve fibers in the white matter, especially the pyramidal tract. Such images are valuable aids in the precise resection of residual lesions of malignant brain tumors near eloquent areas without injuring motor function.

Brain Neoplasms↗
PubMed2004

[Preface: intuitive visualization of medical information].

Information technology(IT), visualization, and manipulation will be the key words for next generation surgery. In other words, it is awaited to make good use of intuitive visualization of medical information management by extensive use of IT in which medical science and engineering are merged and incorporated and of the process management or the visualization of treatment course using three-dimensional intraoperative images and simulation data base. In order to put it into practice, it is inevitable to establish a treatment strategy system that certainly enables surgeons to provide constantly high quality medicine. This means that to achieve the goal while optimizing the strategy toward the goal(a road map) by monitoring real-timely the pre- and intraoperative surgical planning and the operating condition of surgical devices under the control of the surgical strategy system.

Decision Making, Computer-Assisted↗
PubMed2004

[Robotic surgery in neurosurgical field].

Computer-aided surgery commenced in the late 1980s when computer was clinically used for diagnosis and surgical planning. Since then the computer has been used in a surgical navigation system. In the early 1990s a robotic surgery using intelligent manipulator as surgeon's new hands took place. Nowadays intraoperative diagnostic imaging as surgeon's new eyes has become ubiquitous Diagnosis, surgical planning, and navigation are required to be real-timely performed intraoperatively. The time has really come to concurrently diagnose and treat, in which technology visualizing intraoperative medical information and minimally invasive surgery are fused. For that it is necessary to develop a system that real-timely updates information for decision making, and at the same time to present the timely, optimum treatment to be done according to the results of instant evaluation of ongoing treatment. To realize and support above system it is essential to combine a sensor which can precisely distinguishes a focal area from a normal tissue intraoperatively, and a manipulator which participates the treatment. In addition, the manipulator should be accurately controlled using a computer (computer-aided manipulation) according to the surgical plan made by a method aided by a computer (computer-aided design) based on intraoperatively acquired information. It is about to change quality of life to quality of treatment.

Humans↗
PubMed2003

Combined assessment of cardiac systolic dysfunction and coronary atherosclerosis used to predict future cardiac deaths after starting hemodialysis.

BACKGROUND/AIMS: Identification of end-stage renal disease (ESRD) patients at high risk for cardiac events is important for clinical dialysis management. The present study determined whether the combination of cardiac function and coronary atherosclerosis could predict future cardiac events after starting renal replacement therapy (RRT). METHODS: We prospectively assessed left ventricle ejection fraction (EF) and Gensini score (GS) using angiographic severity of coronary atherosclerosis in 88 consecutive ESRD patients [mean age 62 years; 69 males (78%); 55 patients (64%) with diabetic nephropathy] at the initiation of RRT. EF was analyzed by echocardiogram, and GS was scored by coronary angiography within 3 months after starting RRT. The study end point was cardiac death. For analysis of the association between cardiac death and EF and GS measures, the univariate and multivariate Cox proportional hazards model was used. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value, and accuracy of event-free prediction were evaluated. RESULTS: Twenty-four patients (27%) had low cardiac function (EF <50%; low EF) and 44 patients (50%) had severe coronary atherosclerosis (GS >15; high GS). During a follow-up period of 3 years, cardiac death occurred in 21 patients (24%). The PPV of low EF and high GS was 42 and 39%, respectively; the highest PPV (53%) was obtained when low EF and high GS were combined. The cumulative survival rate at 5 years in patients with both low EF and high GS was significantly lower than those with high EF and low GS (91 vs. 22%, p < 0.0005). CONCLUSION: The combined assessment of cardiac function and coronary atherosclerosis at the initiation of RRT strongly predicts future cardiac events.

Cause of Death↗
PubMed2003

Total synthesis of scytophycin C. 1. Stereoselective syntheses of the C(1)-C(18) segment and the C(19)-C(31) segment.

[structure: see text] Stereoselective total synthesis of scytophycin C, a marine 22-membered macrolide displaying potent activity against a variety of human carcinoma cell lines, has been reported in which the polypropionate structure bearing contiguous asymmetric centers was stereospecifically constructed by using new acyclic stereocontrol. This paper describes stereoselective syntheses of the C(1)-C(18) segment (Segment A) including a trans-disubstituted dihydropyran ring and the C(19)-C(31) segment (Segment B) having eight stereogenic centers.

Antineoplastic Agents↗
PubMed2003

Total synthesis of scytophycin C. 2. Coupling reaction of the C(1)-C(18) segment and the C(19)-C(31) segment, a key macrolactonization, and the crucial terminal amidation reaction.

[reaction: see text] Stereoselective syntheses of the C(1)-C(18) segment (segment A) and the C(19)-C(31) segment (segment B) are described in the preceding paper. This paper reports the key coupling reaction of both segments, 22-membered lactonization, and the crucial terminal amidation reaction culminating in the total synthesis of scytophycin C.

Amides↗
PubMed2003

Angiographical severity of coronary atherosclerosis predicts death in the first year of hemodialysis.

BACKGROUND: Cardiac deaths and events tend to cluster within the early-phase after starting dialysis. Our goal is to clarify the influence of severity of coronary atherosclerosis on early-phase death after starting hemodialysis (HD) therapy. PATIENTS AND METHODS: Eighty-three consecutive patients [mean age 62 years; male/female 64/19; diabetic nephropathy in 50 (54%)] with end-stage renal disease who admitted to our hospital to initiate regular HD treatment, and then received coronary angiography within 3 months after first dialysis therapy, were eligible for this study. Angiographical severity of coronary atherosclerosis was scored by numerically using Gensini scoring system. The patients who died within one year from starting HD were compared with those who survived as control by means of logistic regression analysis. RESULTS: Of 83 patients, 12 (14%) died less than one year after starting dialysis therapy. Of these 12 patients, nine died for cardiac causes. Confirmed predictors of death from cardiac cause were older age (>70 years), lower mean blood pressure (<100 mmHg), presence of ischemic heart disease (IHD), myocardial infarction (MI), angina pectoris (AP), chronic heart failure (CHF), poor cardiac function, abnormal wall motion of left ventricule (LV) and angiographical severity of coronary atherosclerosis by univariate model. Adjusting for confounding variables by multivariate model, only severity of coronary atherosclerosis (Gensini score >40 points) had a powerful influence, increasing risk for cardiac cause of early-phase death by about 17 times. CONCLUSIONS: Severity of coronary atherosclerosis predicts death in the first year of HD. These findings suggest that the strategy for prevention of coronary atherosclerosis should be instituted during the early phase of chronic renal failure.

Adult↗
PubMed2002

Favourable long-term outcome by repeated percutaneous coronary revascularization in diabetic haemodialysis patients.

BACKGROUND: Diabetic haemodialysis patients have a high prevalence of coronary events and very high mortality rates. Percutaneous coronary intervention has become a well-established and routine procedure for coronary revascularization. This study investigated the long-term outcome of multiple repeated interventions in diabetic haemodialysis patients with coronary artery disease. METHODS: A retrospective study compared 37 type II diabetic haemodialysis patients with coronary artery disease and 26 non-diabetic patients matched for age, angiographic morphology, and devices of percutaneous intervention. All patients had undergone successful percutaneous intervention prior to enrollment. Percutaneous interventions were repeated in the event of restenosis or the development of a de novo lesion. RESULTS: Diabetic and non-diabetic patients were similar in terms of the number of follow-up angiograms (2.3+/-1.6 vs 2.4+/-1.5/patient) and interventions (2.2+/-1.4 vs 2.2+/-1.5/patient), incidence of target lesion revascularization (85 vs 82%), and number of de novo lesions (15 vs 17%). The cumulative survival rates after the initial percutaneous intervention were similar in the groups (42% vs 31% at 80 months). Cardiac death occurred in 33% of diabetic patients and 42% of non-diabetic patients. Repeated intervention (regression coefficient=16.0, P<0.001) and a lower left ventricular ejection fraction (regression coefficient=-12.9, P=0.047) were determined for the important clinical factors associated with the survival duration after initial coronary intervention. CONCLUSIONS: Multiple repeated percutaneous interventions reduce the long-term mortality of diabetic and non-diabetic haemodialysis patients with coronary artery disease similarly. Multiple repeated percutaneous coronary interventions are a viable option for controlling myocardial ischaemia and improving the long-term outcome in high-risk diabetic haemodialysis patients.

Aged↗